I. Field of the Invention
The present invention relates to the field of paints, pigments, colorants and coatings. More specifically, it provides for novel color compositions and methods of making them.
II. Description of Related Art
In the scientific literature, the term Maya blue refers to a “turquoise” brilliant shade of blue that is found on murals and archaeological artifacts, for example, throughout Mesoamerica. It is described in the literature as being composed of palygorskite clay and indigo, that when mixed and heated, produce the stable brilliant blue color similar to that found in Mesoamerica. Proposed methods of preparation were performed with the intent of trying to replicate the blue color found at the historical sites and to reproduce the techniques employed by the original Maya.
H. Van Olphen, Rutherford Gettens, Edwin Littman, Anna Shepard, and Luis Torres, were perhaps some of the most prominently involved scientists in the examination of organic/inorganic complex paint from the 1960's to the 1980's. In early studies, only Littman and Van Olphen published information specifically on the synthesis of the Mayan organic/inorganic complex (Olphen, 1966a; Olphen, 1996b; Littman, 1980; Littman, 1982). While their work never definitively described the technique for making the colorant, or explained the stability of the organic/inorganic complex, the results of their two decades of studies with respect to the ancient paint laid a foundation of knowledge for future investigators.
Littman has synthesized indigo-attapulgite complexes and verified that his synthetic version was indistinguishable from the original pigments found in the pre-Hispanic murals and artifacts (Littman, 1980; Littman, 1982). The prepared samples had the same physical and chemical characteristics as the authentic Maya blue examined. Littman concluded that the remarkable stability of the attapulgite was due to the heat treatment the attapulgite received during the synthesis. Others have also synthesized compounds similar to that of Maya blue by a number of routes (Torres, 1988). They employed the Gettens test to determine whether the laboratory synthesis of Maya blue was indeed authentic with the same chemical resistant properties (Gettens, 1962). The test was necessary because initial attempts of simply mixing the palygorskite clay produced the color of Maya blue but the mixture did not possess the same chemical properties as the original organic/inorganic complex samples.
The literature for Maya paint compositions does not provide information with respect to varying the color for the paint composition based on altering the pH and particle size; nor does there appear to be mention of using alternate dye or pigment systems as described in the present invention, nor have their been proposed combinations with resins or polymeric systems. The only known literature discussions of pH pertain to the alkaline pH required to reduce the indigo prior to contacting it with the clay (Littman, 1980; Littman, 1982). Furthermore, there is a lack of understanding regarding the chemistry for producing stable and nontoxic paint systems by combining dyes and pigments with fibrous and layered clays.
U.S. Publication No. 2004/0011254 (U.S. Ser. No. 10/370,288), filed Feb. 18, 2003, describes color compositions comprising indigo derivatives pigments and dyes complexed to the surface of inorganic clays. These materials are useful as paints and coatings for artistic and industrial purposes, including use in cements, plastics, papers and polymers. Upon grinding and heating the organic and inorganic component as solid mixtures or in aqueous solutions, the resulting color compositions have unprecedented stability relative to the original starting material. The inorganic component may be either a layered clay or a fibrous clay, such as palygorskite clay, sepiolite clay, kaolinite clay, bentonite clay, nontronite clay, or mordenite clay. The color properties may be further altered with pH and/or pigment size.